This invention relates to an automotive wheel bearing assembly and a method for manufacturing the same.
Among automotive wheel bearing assemblies, there are ones for driving wheels and ones for non-driving wheels. As an example, a wheel bearing assembly for a driving wheel is shown in FIG. 10. It comprises an outer member 3 having two raceways 3a, 3b on its inner peripheral surface, an inner member 1 having raceways 1a, 1b opposite the respective raceways 3a, 3b, and rolling elements 8 disposed between the outer member 3 and the inner member 1 in two rows. A wheel-mounting flange 2 is provided on the outer member 3 or the inner member 1. In the example shown in FIG. 10, the wheel mounting flange 2 is formed on the inner member 1 having a spline hole 9 for a drive shaft in inner periphery thereof.
A brake rotor 20 is fixed by bolts 18 to the side 2a of the wheel-mounting flange 2 of each device. But after assembling, if there should be a runout of the brake rotor 20, with increasing speed of cars, brake vibrations may occur during braking, or brakes may be worn unevenly. Depending on the degree of runout, brake vibrations may occur even at low speeds.
Heretofore, in order to minimize such runout of the brake rotor 20, adjustment of e.g. phase of the bolts which were pressed into the wheel mounting flange 2 with respect to the bolt hole of the brake rotor 20 was necessary. Such a work is troublesome and poor in workability.
Also, if the outer raceway 1a is directly formed on the inner member 1, it is necessary to form a hardened layer 21 on the raceway 1a. Thus, the outer peripheral surface of the inner member 1 is hardened by heat treatment.
Heretofore, when the outer surface of the inner member 1 is heat-treated, a heat-affected layer of the hardened layer 21 on the raceway 1a extends beyond a seal land portion 22 and reaches bolt holes 11 for hub bolts 7 formed in the wheel mounting flange 2.
But, if there exists a heat-affected layer over such a wide range, when the hub bolts 7 are pressed into the bolt holes 11, strain will act on (i.e. distort) the wheel mounting flange 2. This increases the runout of the wheel mounting flange.
If the runout of the wheel mounting flange is large, the brake rotor 20 fixed to the side face 2a by bolts 18 tends to runout. This may cause brake judder and abnormal sound.
An object of this invention is to prevent vibrations and uneven wear of a brake resulting from runout of the brake rotor caused with an increase in the car speed, and to provide a reliable wheel bearing assembly which needs no troublesome runout adjustment when mounting the brake rotor.
Another object of this invention is to provide a wheel bearing assembly which minimizes runout of the wheel mounting flange to prevent brake judder and abnormal sounds.
A still another object of this invention is to provide a constant-velocity joint mounted in a wheel bearing assembly for a driving wheel which is reliable and prevents stick-slip sound.